[CalendarServer-users] How can Attendee know that Organizer does not exist in system anymore

Please pardon my ignorance. I have a question of CalDav Protocol * I have an organizer, 'User1' * I have an attendee, 'User2' * User1 organized an event with User2 * Now User1 got removed from the system. Maybe he did not do any actions on the event he created. His account got removed. How can User2 know that User1 no longer exist and the event in his calendar is invalid??? Regards, Gaurav Jain